Human Physique and Sexual Attractiveness in Men and Women: a New Zealand–U.S

Arch Sex Behav (2010) 39:798–806 DOI 10.1007/s10508-008-9441-y

ORIGINAL PAPER

Human Physique and Sexual Attractiveness in Men and Women: A New Zealand–U.S. Comparative Study

Barnaby J. Dixson Æ Alan F. Dixson Æ Phil J. Bishop Æ Amy Parish

Received: 26 November 2007 / Revised: 30 September 2008 / Accepted: 11 October 2008 / Published online: 13 January 2009 Ó Springer Science+Business Media, LLC 2009

Abstract Men and women living in New Zealand and men expressed preferences for lighter skinned female figures California completed five studies regarding human physi- in New Zealand and California. Results indicate very similar que and sexual attractiveness. In Studies 1–3, women rated preferences for sexually dimorphic physical traits among images of male stimuli and, in Studies 4–5, men rated female men and women of European extraction, living in two cul- stimuli. In Study 1, women in both countries rated meso- turally and geographically different environments. morphic (muscular) and average male somatotypes as most attractive, followed by ectomorphic (slim) and endomorphic Keywords Sexual attractiveness Á Evolution Á (heavily built) figures. In Study 2, amount and distribution of Masculine somatotype Á Feminine waist-to-hip ratio Á masculine trunk hair (chest and abdominal) was altered pro- Penile length Á Secondary sexual traits gressively in a series of front-posed male figures. In both countries, the image lacking any trunk hair was rated as the most attractive, with a steady decline in attractiveness as Introduction hirsutism became more pronounced. Study 3 assessed attractiveness of front-posed male figures that varied only in the Theory suggests that people may (either consciously or length of the non-erect penis. Five lengths were presented: subliminally) use a variety of morphological features to as- The smallest penile size was rated as less attractive than three sess the reproductive quality of potential mates (Barber, intermediate sizes. The largest penile size was not the most 1995; Symons, 1995; Thornhill & Gangestad, 1996). Female attractive, but received higher scores than the unaltered and waist-to-hip ratio (WHR) is a reliable signal of female health smallest penile size. In Study 4, men rated the attractiveness and fecundity, with lower WHR being linked to triggering of back-posed female images varying in waist-to-hip ratio menarche (Lassek & Gaulin, 2007), maintaining regular ovu- (WHR) (from 0.5 to 1.0). The 0.7 WHR figure was rated more latory cycles (Singh, 2002) and efficient storage of the attractive in New Zealand and the 0.6 WHR in California. omega-3 fatty acids required for neural development of the Study 5 measured the attractiveness of female skin color; fetus (Lassek & Gaulin, 2008). WHR is also a significant correlate of female attractiveness, with low WHRs being most attractive to men in North America, the UK, and Ger- many(Furnham,Tan, &McManus,1997;Henss,2000; Singh, B. J. Dixson (&) Á A. F. Dixson 1993a, 1993b). Body Mass Index (BMI) is also significant School of Biological Sciences, Victoria University of Wellington, in determining female attractiveness (Swami & Toveé, 2005a; Wellington, New Zealand Toveé, Maisey, Emery, & Cornellisen, 1999). Larger than e-mail: [email protected] average female breasts are attractive to men (Singh & Young, P. J. Bishop 1995), a trait which may relate to female reproductive poten- Department of Zoology, Otago University, Otago, New Zealand tial, aswomen withlower WHRs and large breasts havehigher fecundity(Jasienska, Ziomkiewicz, Ellison,Lipson, & Thune, A. Parish Gender Studies Department, University of Southern California, 2004). Women with higher follicular phase levels of estradiol Los Angeles, CA, USA also have more attractive faces (Law-Smith et al., 2006). 123 Arch Sex Behav (2010) 39:798–806 799

If human beings have evolved cognitive mechanisms that men are more attractive as romantic partners to women assess visual cues of a potential mate’s health and fecundity, (Hensley, 1994) and men who are taller than average within a then it is necessary to understand what similarities and vari- population sire more offspring in the U.S., UK, and Poland ations exist between cultures. It has been suggested that a (Mueller & Mazur, 2001; Nettle, 2001; Pawlowski, Dunbar, low female WHR is more attractive to men (e.g., WHR = & Lipowicz, 2000). Thus, in Mueller and Mazur’s (2001) 0.7: Singh, 2006); however, some studies do not support this study of military officers in the U.S., taller men were more claim. For example, among the Matsigenka of Peru, a WHR likely to have a fourth child, whereas the median family size of 0.9 was most attractive (Yu & Shepard, 1998). In Bakos- was three for the same study population. siland in rural Cameroon, a WHR of 0.8 was most attractive Nonhuman primates develop capes of hair that depend (Dixson, Dixson, Morgan, & Anderson, 2007b). In Tanzania, upon circulating androgens (Dixson, 1998). In Homo sapi- Wetsman and Marlowe (1999) found that a WHR of 0.9 was ens, mature males display secondary sexual hair to varying most attractive to Hadza men. However, in a more recent degrees on the face, chest and trunk. It has been suggested that study, which presented images of women in which the but- this characteristic may have been retained in males as a visual tocks were visible, Hadza men preferred a WHR of 0.6 signal of sexual maturity (Pagel & Bodmer, 2003). Pronoun- (Marlowe, Apicella, & Reed, 2005). Clearly, further careful ced hirsutism has been found to be highly attractive in the UK cross-cultural investigations are required to understand the (Dixson et al., 2003) but not in China (Dixson et al., 2007a). relation between female WHR and sexual attractiveness. Since variation in the appeal of male body hair may exist Human beings are sexually dimorphic in skin tone (Rob- between populations, more cross-cultural data are required to ins, 1991). Female skin is often lighter than male skin (Dar- measure the importance of this trait. win, 1871; Frost, 1988, 1994; van den Berghe & Frost, 1986). Human male genitalia undergo considerable growth at Natural selection may have been a primary determinant of puberty. First, the testicles enlarge, pubic hair grows, and the lighter skin in women, as vitamin D synthesis is crucial penis increases in length and girth (Tanner, 1978). Much during pregnancy and lactation (Jablonski & Chaplin, 2000). speculation surrounds the role male genitalia may play in Sexual selection may maintain the degree of skin color terms of attractiveness to potential partners (e.g., Miller, dimorphism within populations through males being sexu- 2000) and there is some evidence for the importance of penile ally attracted to females with lighter skin, a theory supported length and girth in women’s judgments of male partner sat- by ethnographic data showing that feminine beauty is as- isfaction (Stulhofer, 2006). Clearly, however, further cross- cribed to lighter skin tone (Aoki, 2002; van den Berghe & cultural studies are required to examine these questions. Frost, 1986). Recently, in a quantitative study of sexual pref- The purpose of this study was to compare the preferences erences among university undergraduates in China, men for morphological features and secondary sexual character- showed a marked preference for images of females with istics in people of European heritage, who have historically lighter skin tones (Dixson, Dixson, Li, & Anderson, 2007a). taken different migratory paths and currently inhabit geo- Cross-cultural studies are limited, however, and the role of graphically different settlements. Europeans began settling skin tone in female attractiveness requires further study. the North island of New Zealand in 1840 and Anglo-Amer- Male physique can be classified according to somatotype icans colonized California following the Mexican war in (Sheldon, Stevens, & Tucker, 1970). Somatotyping is an 1848 (Beck & Williams, 1972; Kirch, 2000). Frequently, anthropometric scaling method for defining physique in cross-cultural research has tested whether humans have relation to muscularity and body fat, employing a three di- evolved mechanisms for assessing mate quality by compar- mensional system which measures a person’s mesomor- ing the preferences of people from very distant cultures. phy (muscularity), endomorphy (fatness), and ectomorphy However, in making cross-cultural comparisons of human (leanness) (Carter & Heath, 1990; Sheldon, Dupertuis, & mate selection, one valid approach is to compare people of McDermott, 1954). Homo sapiens is sexually dimorphic in European origin whose ancestors emigrated to geographi- degree of mesomorphy. While male mesomorphy varies cally separate environments (on opposite sides of the Pacific between populations, within populations men are typically Ocean). If humans have evolved psychological mechanisms more mesomorphic than women (Carter & Heath, 1990). for evaluating potential partners for health and fertility, then Male somatotype is also a significant determinant of sexual the same preferences should be present among people who attractiveness to women, with a mesomorphic muscular share a common ancestry. To test this, we compared sexual physique being highly attractive in the UK, Sri Lanka, and attractiveness ratings for a variety of morphological traits by Cameroon (Dixson, Halliwell, East, Wignarajah, & Ander- people of European origin who currently live in New Zealand son, 2003; Dixson et al., 2007b). and California (USA). In both countries, the subjects selected Darwin viewed sexual selection as operating to enhance were of similar age (predominantly in their teens or 20s), sexually attractive traits and recent studies of Homo sapiens mostly unmarried and of comparable educational level (uni- have provided some supporting evidence. For example, taller versity students). 123 800 Arch Sex Behav (2010) 39:798–806

Method and abdomen). Five images of a front-posed mesomorphic male were presented in random order and each image varied Participants in degree of hirsuteness. Images of mesomorphic males were used because mesomorphy has been shown to be highly A total of 137 men (M age, 20.3 years) and 185 women (M attractive to women (Dixson et al., 2003, 2007b). The dis- age, 20.1 years) constituted the New Zealand sample and 85 tribution of chest and abdominal hair was altered in a step- men (M age, 20.7 years) and 81 women (M age, 20.3 years) wise fashion from none to pronounced hirsutism. Women constituted the U.S. sample. Less than 5% of the participants rated each image using the 6-point scale for sexual attractive- were married. ness. Study 3 examined female preferences for male images Procedure varying in length of the (non-erect) penis. Penis length was altered on five front-posed mesomorphic males (the same Each questionnaire began with a cover sheet to collect mesomorphic image used in Study 2). Each image was pre- demographic information from each participant, including sented in random order and rated using the 6-point scale for sex, age, ethnicity, and marital status (married or single). All sexual attractiveness. In one figure, the penis was the same questionnaires were anonymous and participation was size as the original photograph used to model the images in voluntary. the computer. In the remaining four images, we altered penile Images of males were produced by scanning photographs lengths. Originally, we had intended to alter the four lengths of front and back-posed males from Sheldon et al. (1954). In to represent 80%, 120%, 130%, and 140% of their original each case, images from the mid-range of three somatotypes size. However, measurements of the actual figures produced (mesomorphic, ectomorphic, and endomorphic) were used, revealed images to be 78%, 122%, 133%, and 143% of the as well as a man of average somatotype. We did not modify original size. these images to control for possible differences in fluctuating Study 4 measured male preferences for a replicated female asymmetry. Images of women were the same as those used in image varying only in WHR; the WHR range was: 0.5, 0.6, previous studies (Dixson et al., 2007a, 2007b). Any asym- 0.7, 0.8, 0.9, and 1.0. The images were arranged in random metries present in the original images of both sexes have been order on the same sheet of the questionnaire. Participants retained and it is possible that such differences might have were asked to choose only the image they found most sexu- affected attractiveness ratings to some degree. The scanned ally attractive. On a subsequent page, the same range of images of males and females were then manipulated using WHRs was shown, this time asking males to choose the im- Photoshop 7.0 and standardized for height, posture, and for age they found most sexually attractive for a long-term studies 1–4, color. Skin color was matched to a European relationship. Caucasian sample by scanning photographs from Anatomy Study 5 assessed male preferences for female images for the Artist (Simblet, 2001) into the computer and matching varying in skin color. Five color variations of the same back- skin color of the images to these photographs in Photoshop posed female figure (WHR 0.8) were used in this study. Skin 7.0. Where front-posed images were used, faces were blacked tone was altered (using Photoshop 7.0) in a step-wise fashion out, as our studies did not concern facial stimuli. (by 10 units of brightness and 15 units of contrast) to create two images that were darker and two images that were lighter Measures than the original. The images were placed in random order on a single page and men were asked to select only the image For Studies 1–3, women used a 6-point Likert scale to score they found most sexually attractive. ratings of attractiveness where 0 = unattractive, 1 = only slightly attractive, 2 = mildly attractive, 3 = moderately attractive, 4 = very attractive and 5 = extremely attractive. Statistical Analysis In Studies 4–5, men chose the female image that they found most attractive for either a short-term or a long-term In Studies 1–3, a two-way mixed model analysis of variance relationship. (ANOVA), with culture as the between-subjects factor and Study 1 measured female preferences for back posed male stimulus as the within-subjects factor, was used evaluate the images varying in somatotype (ectomorph, endomorph, attractiveness ratings. In Studies 4–5, the responses of men in mesomorph, and average). Images were presented in random both cultures were compared using a likelihood ratio (G- order and women rated each image using the 6-point scale for square) test with culture crossed with stimulus. If differences sexual attractiveness. in male preferences across cultures occurred, the table was Study 2 assessed female preferences for front-posed male partitioned according to Agresti (2002) in order to carry out images varying in degrees of hirsuteness on the trunk (chest pair-wise comparisons. 123 Arch Sex Behav (2010) 39:798–806 801

Study 1: Female Preferences for Back-Posed Male Images significant Nationality main effect or a Nationality 9 Hir- Varying in Somatotype sutism interaction. Post-hoc Scheffe´ tests showed that the most attractive image was the male figure lacking any chest Figure 1 shows the mean attractiveness ratings as a func- or trunk hair and main effects were due to steady declines tion of nationality and body type. A 2 (Nationality) 9 4 in attractiveness ratings as images became more hirsute (Somatotype) ANOVA revealed a significant main effect (Fig. 3). for Somatotype, F(3, 795) = 532.49, p \ .0001, but there was no significant Nationality main effect or a significant Study 3: Penile Size and Attractiveness Somatotype 9 Nationality interaction. Post-hoc Scheffe´ tests showed that the male images depicting mesomorphic A 2 (Nationality) 9 5 (Penile size) ANOVA revealed sig- and average somatotype were rated as significantly more nificant main effects for Penile size, F(4, 1060) = 218.06, attractive than the ectomorphic and endomorphic somato- p \ .0001 and a significant Nationality 9 Penile size inter- types (all ps \ .001). The mesomorphic image was rated as action F(4, 1060) = 21.74, p \ .0001. Post-hoc Scheffe´ the most attractive but not more so than the average tests showed significant interactions of the repeated measure somatotype. were due to higher attractiveness scores in California for the images depicting penile lengths 122%, 133%, and 144%, Study 2: Female Preferences for Male Images Varying which were rated as significantly more attractive than penile in Hirsuteness lengths of 78% and 100% (p \ .0001 for each paired com- parison). In New Zealand Scheffe´ tests showed that penile Figure 2 shows the mean attractiveness ratings as a function lengths of 122% and 133% were more attractive than the of nationality and body type. A 2 (Nationality) 9 5 (Hir- 78%, 100% or 144% images (p \ .0001 in each case). sutism) ANOVA revealed a significant main effect for hirsutism, F(4, 1060) = 175.09, p \ .0001, but there was no

Fig. 1 Women’s mean ratings (?SEM) for sexual attractiveness of Fig. 2 Women’s mean ratings (?SEM) for attractiveness of front- back-posed male ﬁgures of four different somatotypes: ENDO = endo- posed male ﬁgures which vary only in hirsuteness of the trunk (chest and morphic; ECTO = ectomorphic; MESO = mesomorphic; AVER = abdomen). None = no trunk hair; Max = pronounced hirsuteness. average body build. ***p \ .001 **p \ .01; ***p \ .001 123 802 Arch Sex Behav (2010) 39:798–806

Table 1 Male preferences for female waist-to-hip ratio (WHR) for attractiveness (A) and long-term relationship (B) WHR Culture Total NZ U.S.

A. 0.5 Count 1 13 14 % Within culture 8% 15.3% 6.8% 0.6 Count 45 43 88 % Within culture 37.5% 50.6% 42.9% 0.7 Count 47 18 65 % Within culture 39.2% 21.2% 31.7% 0.8 Count 27 11 38 % Within culture 22.5% 12.9% 18.5% B. 0.5 Count 1 10 11 % Within culture 8% 11.8% 5.4% 0.6 Count 30 42 72 % Within culture 25% 49.4% 35.1% 0.7 Count 51 21 72 % Within culture 42.5% 24.7% 35.1% 0.8 Count 38 12 50 % Within culture 31.7% 14.1% 24.4%

WHRs of 0.5 and 0.6 compared to men from New Zealand who preferred WHRs of 0.7 and 0.8. Fig. 3 Women’s preferences for images of male figures varying only in Men in both cultures were then asked to select the WHR length of the (non-erect) penis. Images are in order of increasing size. they found most attractive for a long-term relationship. Due Data are means (?SEM) ***p \ .001 to the absence of selections of the 0.9 and 1.0 WHRs, a 2 (Nationality) 9 4 (Waist-to-hip ratio) G2 test was conducted. Table 1 also shows the results of this test, which Study 4: Men’s Ratings of Female Waist-to-Hip Ratios showed a significant association between WHR preferences and culture (G2 = 31.65, df = 3, p \ .0001). When com- Due to the absence of selections of the 0.9 and 1.0 WHRs, paring selections for a WHR of 0.7–0.8 there was no signif- a 2 (Nationality) 9 4 (Waist-to-hip ratio) G2 test was con- icant association (G2 = 0.403, df = 1, p = .526). When ducted. The results revealed a significantassociation between comparing a WHR of 0.6 to WHRs of 0.7 and 0.8 there was a culture and preference for WHR (G2 = 26.60, df = 3, p \ significant association between stimuli and culture (G2 = .0001; Table 1a). To uncover where the differences in pref- 18.63, df = 1, p \ .0001), with men from the USA prefer- erences occurred, the table was partitioned in order to carry ring a lower WHR of 0.6 compared to men from New Zealand out pair-wise comparisons. When comparing selections for a who preferred WHRs of 0.7 and 0.8. When comparing male WHR of 0.7–0.8 there was no significant association (G2 = preferences for a WHR of 0.5 to preferences for WHRs 0.6, 0.019, df = 1, p = .891). When comparing a WHR of 0.6 to 0.7 and 0.8, there was a significant association (G2 = 12.60, WHRs of 0.7 and 0.8 there was a significant association be- df = 1, p \ .0001) with men from the USA gave higher tween stimuli and culture (G2 = 8.69, df = 1, p = .003), selections for a 0.5 WHR when compared to men from New with men from the USA preferring a lower WHR of 0.6 Zealand. In general, men from the USA preferred lower compared to men from New Zealand who preferred WHRs of WHRs of 0.5 and 0.6 compared to men from New Zealand 0.7 and 0.8. When comparing male preferences for a WHR of who preferred WHRs of 0.7 and 0.8. 0.5 to preferences for WHRs 0.6, 0.7 and 0.8 there was a significant association between culture and stimuli (G2 = Study 5: Men’s Ratings of Female Skin Color 17.83, df = 1, p \ .0001). Men from the USA gave higher selections for a 0.5 WHR when compared to men from New Table 2 shows the results of a 2 (Nationality) 9 5 (Skin color) Zealand. In general, men from the USA preferred lower G2 test, which revealed a significant association between 123 Arch Sex Behav (2010) 39:798–806 803

Table 2 Male preferences for female skin tone heavily built (endomorphic) masculine images as least attrac- Skin tone Culture Total tive, the same result as obtained in the UK, Sri Lanka, Cam- eroon, and China. NZ U.S. Somatotyping is useful in assessments of physical fitness, Lightest Count 20 8 28 including strength, coordination, and endurance. Mesomor- % Within culture 16.7% 9.4% 13.7% phic males are more successful in physical fitness tests, while Lightest Count 37 47 84 ecto-mesomorphs perform best at distance running and endo- % Within culture 30.8% 55.3% 41% mesomorphs excel at strength-testing sports (e.g., weight Average Count 50 26 76 lifting). Endomorphic males exhibit the lowest levels of % Within culture 41.7% 30.6% 37.1% performance in all these areas (Carter & Heath, 1990). Meso- Darker Count 10 2 12 morphy is also associated with better cardiac function, espe- % Within culture 8.3% 2.4% 5.9% cially when compared to men who have an endomorphic constitution (Katzmarzyk, Malina, Song, & Bouchard, 1998). Darkest Count 3 2 5 During human evolution, natural selection may have favored % Within culture 2.5% 2.4% 2.4% masculine traits underlying strength and endurance running as well as intellectual traits which are important for hunting selection and culture (G2 = 14.24, df = 4, p = .007). When and foraging. These factors may have influenced men’s comparing male preferences for the darker and darkest skin ability to succeed in the hunter-gatherer societies from which tones there was no significant association (G2 = 1.00, df = 1, modern humans evolved (Bramble & Lieberman, 2004; Buss, p = .31). This trend continued when comparing male prefer- 2003; Marlowe, 2004). An average body build may be better ences between average skin tone and the two darker skin tones adapted for endurance running, while muscularity may signal (G2 = 0.758, df = 1, p = .38). When comparing male pref- ability to protect a potential mate and to succeed in inter-male erences for the image one degree lighter than average with competition (Buss, 2003). Although the ecological factors average and darker skin tones, there was a significant associ- which selected for such masculine traits are not as important ation (G2 = 10.16, df = 1, p \ .0001) with men from the in contemporary industrialized societies, sexual selection USA preferring the lighter skin tone. No significant associa- during human evolution may explain deep-seated female tion was found when comparing the lightest skin tone to the preferences for certain masculine somatotypes. lighter, average and darker skin tones (G2 = 2.30, df = 3, Compared to many non-human primates, adult human p = .129). males exhibit relatively well developed secondary sexual traits (e.g., facial and body hair), such as occur in polygynous Discussion species (Dixson, Dixson, & Anderson, 2005). Pagel and Bod- mer (2003) have suggested that natural selection favored the The study populations examined here comprised mostly evolution of hairlessness in Homo sapiens, as an adaptation to young women and men who were attending universities in reduce ecto-parasite loads, but that hair was retained in cer- New Zealand and California. Despite the limitations of the tain areas of the body due, in part, to effects of sexual sample, the results obtained provide some useful insights selection. Initial studies, conducted in the UK, showed that concerning visual cues and human sexual attractiveness. masculine trunk (chest and abdominal) hair was rated as The female preferences for male somatotypes reported highly attractive by women (Dixson et al., 2003). However, here confirm the findings of previous studies conducted in the the current study, involving people of European descent UK, Sri Lanka, and Cameroon (Dixson et al., 2003, 2007b). living in New Zealand and California, produced the opposite A muscular (mesomorphic) male somatotype was rated as result. Images of men lacking trunk hair were rated as most most attractive by women, followed by an average physique. attractive, with a progressive decline in scores as hirsutism Indeed, in New Zealand and California, ratings for these increased. Similar results were obtained in China (Dixson somatotypes did not differ statistically. In China, by contrast, et al., 2007a), while in Cameroon hirsutism had little effect an average physique was rated as more attractive than a on women’s ratings of male attractiveness (Dixson et al., mesomorphic physique (Dixson et al., 2007a). Therefore, 2007b). Currently, there is little support for the hypothesis while broad shoulders, narrow waistline, high shoulder-to- that sexual selection may have influenced the evolution of hip ratio, and defined musculature are clearly important masculine trunk hair via female mate choice. Cross-cultural traits influencing female assessments of male physical attrac- studies should continue to examine this question and to col- tiveness (Hughes & Gallup, 2003; Lynch & Zellner, 1999; lect data from women in older age groups. There is some Swami & Toveé, 2005b), it is not the case that muscularity is evidence that younger males in the U.S. are more likely to necessarily paramount to female ratings of male somato- practice hair removal from the body. Thus, a study of 118 types. In both New Zealand and California, women rated male undergraduate students at the University of South 123 804 Arch Sex Behav (2010) 39:798–806

Florida found that 64% of men were practicing depilation the evolution of lighter skin coloration in women may have (Boroughs, Cafri, & Thompson, 2005). Although the occur- been influenced by sexual selection (Darwin, 1871; van den rence of depilation was not measured in the current study, it Berghe & Frost, 1986). may have influenced our results given the younger ages of It is possible, although it remains to be determined, that most participants. skin color may interact with hair color to influence male In its flaccid state, the human penis is displayed more perceptionsoffemaleattractiveness. Thus,womenwith blond prominently than is typical of the non-human primates, as it hair and tanned skin may appear darker than a brunette with protrudes from the body, it is surrounded by pubic hair, and is the same skin tone. Further research is required to examine more readily visible due to men’s upright (bipedal) gait. It has this question. Furthermore, subtle changes in female skin tone been suggested that penile traits may have been influenced by may occur during menstrual cycles (Roberts et al., 2004) sexual selection during human evolution (Potts & Short, and women’s complexions may reflect differences in estroge- 1999; Short, 1980), although little attempt has been made to nic effects upon cues which influence attractiveness (Fink, test this hypothesis. In the current studies, women in New Grammer, & Matts, 2006; Law-Smith et al., 2006). Further Zealand and California rated images of the same male as cross-cultural studies to measure the effects of female skin more, or less, attractive depending upon variation in length tone upon attractiveness and the relevance of naturally occur- of the (non-erect) penis. Although numerical ratings were ring sex differences in skin coloration would be valuable. somewhat higher in the U.S. sample, women in both coun- Female WHR was an important determinant of male pre- tries gave the highest ratings to images in which the penis had ferences in both New Zealand and California. The female been lengthened moderately (by 22% and 33%) but rated image depicting a WHR of 0.6 was most attractive to men in extremes of penile length (78% and 143% of normal) as less California, both for attractiveness ratings and when consid- attractive. It may be that such preferences reflect female ering a long-term relationship. A WHR of 0.6 and 0.7 re- judgments of what is healthy and normal in a male, while the ceived significantly higher scores for attractiveness in New smallest, and the greatest, penile lengths may be perceived as Zealand. However, when a long-term relationship was con- aesthetically abnormal. Penile width was not altered in these sidered, men no longer preferred a female WHR of 0.6; in- studies, although there is some evidence that both the width stead, more participants chose the images with WHRs of 0.7 and length of the penis influences women’s partner satis- and 0.8. This suggests that men may alter their mate prefer- faction (Stulhofer, 2006). The results from New Zealand and ences when considering long-term relationships, as is the U.S. were similar to those obtained in Cameroon and thought to be the case for some other female traits (Buss & China (Dixson et al., 2007a, 2007b). The (still limited) cross- Schmidt, 1993). cultural evidence indicates that penile size has some signif- Research using line drawings has been criticized for not icance in women’s judgments of male attractiveness. representing significantly realistic images of human phy- Skin color varies consistently between human popula- sique, and for confounding possible effects of WHR and BMI tions, so that natural selection may have favored reduction in upon female attractiveness (Toveé & Cornelissen, 2001). dark (melanic) skin pigmentation in more northerly latitudes, These are valid criticisms. The results reported here are con- due to low UV exposure and constraints upon vitamin D sistent with Singh’s (1993a) theory that female WHR may act metabolism (Jablonski, 2006; Jablonski & Chaplin, 2000). as a first pass filter in men’s judgments of female attractive- Sexual dimorphism in skin tone has been reported in a ness, as WHR provides a reliable cue to reproductive health number of ethnic groups, with women typically having a and fecundity (Singh, 2002, 2006). However, the images we lighter skin tone than men (Darwin, 1871; Frost, 1988, 1994). used in studies conducted in New Zealand, the U.S., and Skin condition may be a visual cue to female health and elsewhere do not allow a distinction to be made between the reproductive condition, as lightening of skin color occurs relative importance of female WHR and BMI in men’s judg- with the onset of physical maturity (Tanner, 1978). Preg- ments of attractiveness, as the two variables are positively nancy and lactation may bring about localized changes in correlated. What is clear, however, is that despite living in skin pigmentation, which persist as women age (Symons, different cultural and physical environments, young men and 1995). In the current study, men rated images with lighter women in New Zealand and California exhibit consistent and skin tones as most attractive, especially so in the Californian very similar preferences for sexually dimorphic traits impor- sample. In New Zealand, men rated the female images of tant for mate choice. average skin color as most attractive, followed by the image which was lightened by 10 units of brightness and 15 units of Acknowledgements We would like to thank all the students who re- contrast. This latter image was the most attractive to Cali- sponded to the questionnaires at Victoria University of Wellington and Otago University of Dunedin in New Zealand and the University of fornia men. Male preference for lighter female skin tones was Southern California, Los Angeles, California. We also thank three also significant in studies conducted in China (Dixson et al., anonymous reviewers and the Editor for most constructive criticisms of 2007a). Hence, our results lend support to the hypothesis that the original manuscript. 123 Arch Sex Behav (2010) 39:798–806 805

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